# dno fitting new tails to existing.

#### 17thman

went to 1970's flat today. Customer wants lighting circuits rewired with additions, accent and mood lighting etc. Upon opening their external meter housing and also looking at the cu the tails are 10mm. but in in the meter housing the dno have installed new tails from intake to meter and and then from meter they have run 25mm tails into floating henly blocks joining to the 10mm tails which dissappear 2m upwards and into the flat.

They have a 60 amp main fuse so 10 tails are fine in principle but the maximum demand is well over 60A So they need a new service fuse and tails. No problem but my questions are. If the dno come to fit the new fuse and, or not, isolator. can they just continue with the practice of these floating henleys to lower conductor sizes. Was the work initially compliant? I understand that a fuse would be required at the point a lower current carrying capacity joined the initial conductor. I would estimate the length of the 10mm tails to be no less than 4m.

Thankyou

#### jason1958

Why do you say maximum demand well over 60A?
Has the BS1361 fuse ever blown? BS88 fitted?

1 - Diversity calculations help - except shower, immersion, storage heaters

2 - DNO generally will only u/g to 80A rather than 100A these days

3 - If this is a flat there may be mitigating circumstances re 60A

DNO "tails" used to get quite creative - big 25mm 2c with armour hose-clipped over copper pipe, not even a BW gland in site, so beware what you ask for

#### 17thman

wont type all calcs, she has shower, elec hob, underfloor heating, immersion, 2 ring finals and lighting = @ 100A, obviously needs new tails. that is a given. Yes you are correct, earth from pme/met connected to copper pipe housing the 10mm tails and then clamped at cu end into earth bar. My question related to the dno behaviour and the fusing down

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